118 Letters to the Editor

Fig. 2. Electron micrographs of pseudo gray platelets. (A) Blood collected into EDTA showing absence of storage granules (×15,000). (B) Blood collected into the trisodium citrate dehydrate-containing tube showing normal platelet structures, including typical -granules (×12,000). collected into the sodium citrate-containing tube, which showed normal platelet counts. Only a few cases of PGPS have been reported [1-4]. To our knowledge, this is the first case to be reported in Korea. Stavem and Berg [1] described EDTA-induced ‘platelet stain preventing factor’, and Mant et al. [2], Cockbill et al. [3], and Toyota et al. [4] reported platelet degranulation caused by EDTA. Unlike GPS, which is a rare inherited disorder of the megakaryocytes characterized by loss of the -granule stor-age pool of proteins in platelets and causing bleeding ten-dency [5], PGPS is an in vitro phenomenon showing EDTA-induced pseudothrombocytopenia with no bleeding tendency. The typical EM finding of PGPS is degranulation of EDTA-exposed platelets. Mant et al. [2] reported cases of EDTA-induced platelet degranulation with aggregation caused by a ‘plasma factor’ which was not IgG, IgM, fibrinogen or albumin. They thought it was an unidentified abnormal plasma component which, on exposure to EDTA, develops ‘anti-platelet activity’. Cockbill et al. [3] reported that the ‘plasma factor ’ causing platelet degranulation could be an immunoglobulin but clear-ly different from the EDTA-sensitive antibodies which cause platelet aggregation and agglutination. The mechanism by which platelet degranulation occurs in PGPS remains unclear